1. Field of the Invention
The present invention relates to a machine and a method for reaming a bore in a tubular member. More particularly, it relates to an electrically controlled and actuated machine for reaming gun barrels and further finishing the bore of the barrels of handguns, rifles, and shotguns.
2. Description of Related Art
A gun barrel is a tube through which a controlled explosion or rapid expansion of gases are released in order to propel a projectile out of the end of the gun barrel. To be effective a gun barrel must be able to hold the expanding gas produced by the propellants to ensure that the projectile is propelled at sufficient velocity. Referring to FIG. 1, a gun barrel 10 defining a bore 12 is shown. Ideally, the bore 12 of the gun barrel 10 is perfectly straight, as shown, with no deviations in diameter; however, it is very difficult to produce gun barrels with the extremely straight and highly honed bores that result in optimum performance characteristics. Therefore, perfectly straight and perfectly honed bores while ideal are not currently achievable, and some deviations 14 in the gun barrel bore 12, shown exaggerated in phantom, are present in every gun barrel 10.
FIG. 2 shows a cross-sectional view of a rifled gun barrel 10 which has helical grooves 15 in the bore 12 to impart a spin to the projectile along its longitudinal axis. The bore 12 has a minor diameter 16 and a major diameter 18. The barrel 10 has a minor bore diameter 16 that is generally equal to the caliber of the finished rifled barrel 10. For example, a typical finished .30 caliber rifle barrel constructed to precision standards has a major diameter 18 (groove-to-groove) of 0.308 inches and a minor diameter 16 (land-to-land) of 0.300 inches. In another example, a typical finished twelve gauge smoothbore shotgun barrel constructed to precision standards has a bore diameter of 0.729 inches.
In spite of the great care given to making straight holes, gun barrel makers normally further process the bore 12 following drilling to smooth the surface, correct minor variations in straightness, and establish the final bore diameter 16.
A reamer is used to reduce the roughness inherent in the drilled bore. A reamer includes a long cutting tool with its working edges on the sides. The maximum diameter of the reamer is typically the same as the final bore diameter. To assure proper alignment and straightness of the cutting tool as it passes through the barrel, the length of the reamer is much greater than its diameter. A typical reamer for refining the bores of gun barrels will have a length that is ten to twenty times its diameter for precision alignment. Because the reamer is required to remove very little metal, the working edges are finely honed.
However, although the inner surface of the barrel bore is significantly smoothed by reaming, residual markings that may ultimately be passed to a fired projectile can remain.
In an attempt to produce perfectly straight and perfectly honed bores, many gun barrel reamers are purposely built to produce a particular caliber gun barrel with a particular outside diameter and a particular length, thereby limiting the range of barrels that can be produced from a particular gun barrel reamer.
Furthermore, in many gun barrel reamers, the speed of rotation of the reamer and the movement speed of the barrel over the reamer are often not constant throughout the reaming process which produces bores that are less straight and less well honed than possible.
In view of the above, there is a need for a barrel reaming machine that can ream gun barrels with a variety of lengths and outside diameters and is capable of producing a variety of bore diameters that are straight and finely honed in these gun barrels.